Tantalum

Symbol: Ta
Atomic Number: 73
Atomic Weight: 180.9479
Element Classification: Transition Metal
Discovered By: Anders Ekeberg
Discovery Date: 1802 (Sweden)
Name Origin: King Tantalus of Greek mythology, father of Niobe.

Density (g/cc): 16.654
Melting Point (K): 3269
Boiling Point (K): 5698
Appearance: Gray, heavy, hard metal
Atomic Radius (pm): 149
Atomic Volume (cc/mol): 10.9
Covalent Radius (pm): 134
Ionic Radius: 68 (+5e)
Specific Heat (@20C J/g mol): 0.140
Fusion Heat (kJ/mol): 24.7
Evaporation Heat (kJ/mol): 758
Thermal Conductivity (@25C W/m K):
Debye Temperature (K): 225.00
Pauling Negativity Number: 1.5
First Ionizing Energy (kJ/mol): 760.1
Oxidation States: 5
Electronic Configuration: [Xe] 4f14 5d3 6s2
Lattice Structure: Body-Centered Cubic (BCC)
Lattice Constant (): 3.310
Lattice C/A Ratio: n/a

Mineral Hardness [no units]: 6.5
Brinell Hardness [/MN m-2]: 800
Vickers Hardness [/MN m-2]: 873

Note: Tantalum is softer than some other refractory metals and more difficult to prepare as it easily forms damaged layers in sectioning and grinding. Some alloys can be cold worked easily, although they do not work harden appreciably, so it may be difficult to get completely deformation-free microstructures. Attack-polishing additions can be made to the final polishing abrasive slurry, or vibratory polishing may be employed. Tantalum may contain hard phases that promote relief control problems as well.

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